Hi centraly,

something affects wpForo Editor because wpForo editor doesn't have such problem. The issue is how to find the problem causer. We can't do so deep debugging on your website, we'll need access to everything and it may take days. The best way is installing a test/fresh WordPress in e.g. /test/ subdirectory, then install wpForo, then the current theme and so on... you'll find the step where this problem comes. This is the best and fastest way to debug this site specific issue. Just don't forget to check the editor after each step.

Maybe try other theme this can be a theme conflict.